The purpose of this study is to determine whether oral docosahexaenoic acid (DHA) supplementation is beneficial to patients with Long-Chain-3- Hydroxyacyl-coA Dehydrogenase Deficiency (LCHADD), an inborn error in fatty acid metabolism. The following hypothesis is to be tested: Supplementation of DHA, as an adjunct to treatment with a low fat, medium-chain triglyceride (MCT) supplemented diet, will retard or prevent the early development of retinal degeneration in patients with LCHADD. Patients will be supplemented with DHA for one year. DHA status will be measured by plasma and red blood cell fatty acid analysis. Deficient DHA levels will be normalized and maintained throughout the supplementation period. Electroretinograms (ERG) and visual evoked potentials (VEP) will be measured at baseline, after six months of supplementation and after twelve months supplementation. Efficacy will be measured by normalization of plasma levels of DHA and improvement in ERG and/or VEP results.